* {
  margin: 0;
  padding: 0;
}

a {
  text-decoration: none;
  color: white;
}

li {
  list-style-type: none;
}

nav, .nav-submenu-list {
  background-color: #25383C;
}

.nav-list-item a {
  color: white;
  display: block;
  padding: 20px 40px;
}

.nav-submenu-list {
  display: none;
}

/*
  按钮部分样式:
*/
.menu-btn {
  border: none;
  padding: 8px 0;
}


.menu-btn:after {
  content: '';
  display: block;
  clear: both;
}

.menu-btn-icon {
  border: none;
  width: 30px;
  height: 30px;
  background-image: url("../images/menu.png");
  background-position: center center;
  background-repeat: no-repeat;
  background-size: cover; /*保证背景图片始终覆盖容器*/
  cursor: pointer;
  float: left;
  margin-left: 10px;
}

#collapseBtn {
  display: none;
}

#collapseBtn:checked + .nav-container-list {
  display: block;
}

.nav-container-list {
  display: none;
}

#collapseBtn:checked ~ .menu-btn > .menu-btn-icon {
  background-image: url("../images/menu.png");
}


@media all and (max-width: 480px) {
  .flex-row {
    flex-direction: column;
  }

  .nav-list-item {
    text-align: center;
  }
}

@media all and (min-width: 480px) {

  .nav-list-item {
    position: relative;
  }


  .nav-submenu-list {
    display: none;

    position: absolute;
    left: 0;
    top: 100%;
  }

  .nav-container-list {
    display: flex;
    max-width: 1280px;
    margin: 0 auto;
  }

  /*别忘了，在桌面导航中我们是不需要收起按钮*/
  .menu-btn-icon {
    display: none;
  }

  .menu-btn{
    padding: 0;
  }


}

















